Film Properties (4)

Question 1

What materials construct radiographic film?

Answer 1

• Clear polyester
• Flexible transparent base
• Silver halide gelatin emulsion coating

Question 2

Film should be:

Answer 2

• Water and chemical resistant
• non-combustable
• designed to promote easy drying

Question 3

Define Latent Image

Answer 3

When exposed to radiation the silver halide emulsion changes in physical structure. This change can only be detected when the film is developed.

Question 4

Black Metallic Silver

Answer 4

Once developed, a reaction causes the exposed silver grains convert into “black metallic silver”.
- the degree of darkening (amount of blackening) that occurs constitutes the formation and visibility of the final image.

Question 5

Why are both sides of film coated with emulsion? (Double coating)

Answer 5

1. increase amount of silver halide - speed up latent image

2. both sides can be facing upward during exposure

Question 6

Why are single coated films used?

Answer 6

extremely fine grains with a slower exposure time, meant for critical inspections that require an exceptional amount of detail.

Question 7

Define Substrate/Subbing Layer

Answer 7

The layer between the clear film base and the emulsion on film.
- a solvent based adhesive to hold the silver halide to the film base

Question 8

Define Super-coat Layer

Answer 8

outer layer or top coat made of a protective gelatin meant to protect the emulsion from scratches and pressure.

Question 9

What is the film base made of?

Answer 9

Thick layer of clear polyester or polycarbonate (or cellulose tri-acetate) with a small amount of blue dye. Provides a robust/rigid yet flexible foundation.

Question 10

During processing, emulsion layers ___ __ the chemical mixtures and swell.

Answer 10

soak in

Question 11

During the film drying process, the emulsion _____ perpendicular to the film surface.

Answer 11

contracts